164 CATALOGUE OF THE BLASTOIDEA. 



rounding it, and in each case forming a separate little dome l . Hambach 2 says, 

 however, that Shumard's original specimen "does not show anything of the remark- 

 able structure represented in the figure. It is a specimen from Spergen Hill, Ind., 

 and a number of specimens from the same locality as well as those from Greencastle, 

 Ind., also a small variety found in the upper layers of the Chester or Kaskaskia 

 Limestone, frequently present the same appearance — which, however, is due to the 

 oolitic character of the rock in which they are imbedded. This induced me to call 

 them ' ovulum-like bodies.' " 



We presume that we are correct in supposing the last " them " to refer, not to the 

 specimens and variety which are included in the previous " they,"' but to " the minute 

 plates of Pentrcmites conoidens (sic) described and figured by Shumard," of which 

 Hambach makes mention on the page preceding that from which we have quoted. 

 Not having seen Shumard's specimen, we can offer no opinion as to the accuracy of 

 Hambach's statements respecting it. But so far as the central group of plates is 

 concerned at any rate, we cannot help thinking that the analogies of Elwacrinus, 

 Granatocrinus, Orophocrinus, and Schizoblastus are all in favour of Shumard's de- 

 scription, as we have remarked on p. 08. 



It may be noted further that Mr. Billings 3 said : — "In a specimen of the same 

 species sent me by Mr. Lyon, in which those plates are partly preserved, I find that 

 there is a small pore in each of the five angles of the central aperture ; " and he 

 rightly added, that " the five ambulacral grooves enter the interior through these 

 pores," the presence of which was independently and almost simultaneously suggested 

 by Messrs. Meek and Worthen in the following words: — " We think it possible that 

 small openings exist under this latter group of plates (*'. e . central dome) at the upper 

 terminations of the ambulacral furrows 4 ." 



It must not, however, be forgotten that McCoy had perhaps already observed similar 

 openings, for in his description of the genus Pentremites he says, " 1 think I observe 

 ocular pores at the oral ends of the ambulacra 5 ." McCoy, however, referred to Pen- 

 trcmites, forms which we now know to be species of Granatocrinus (e. g. Pentremites 

 campanulatus, P. Derbiensis, and P. ellipticus), but we do not think that these some- 

 what doubtful pores can have been "ambulacral openings;" for a covered summit is 

 unknown in any British Blastoid. 



Both Pentrcmites conoidens and its variety Koninckanus are remarkable for the 

 large proportion of the hydrospire apparatus which is enclosed within the substance 



1 Trans. St. Louis Acad. Sci. 1858, vol. i. no. 2, p. 243, pi. 9. fig. 4. 



2 Trans. St. Louis Acad. Sci. 1884, vol. iv. no. 3, pp. 540, 541. 



3 Amer. Journ. Sci. 1869, vol. xlviii. p. 82; Ann. & Mag. Nat. llist. 1S70, vol. v. p. 265. 



4 Proc. Acad. Nat. Sci. Philud. 1869, p. 85. 

 * Brit. Pal. Foss. fasc. 1, 1851, p. 123. 



